Stability of optical elements in the NIF target area building

Le résumé fourni par la source

The Target Area Building (TAB) of the National Ignition Facility (NIF) is 300 feet long, 100 feet wide, and 100 feet tall and is comprised of a cylindrical target building and two switchyard space frames. The reinforced concrete target building houses the target chamber, target positioner, turning mirrors, final optics assemblies, and diagnostics, while the steel switchyard space frames support turning mirrors and diagnostic equipment. Within the TAB, the 192 independent laser beams of the NIF laser system are required to be accurately positioned. In order to satisfy the engineering system requirement for optical system positioning (stability on target), the TAB must provide a stable platform for optical elements before and during a shot. This paper summarizes the stability analyses that were performed in support of the TAB and optical system design. Sources that influence optic stability are structural excitations, such as ambient and wind induced vibrations, and thermal transients, such as diurnal and HVAC temperature changes. A positioning error budget has been developed for the NIF project for use in the design and evaluation of structures which support optical elements. To satisfy the error budget requirements, vibrational stability will be achieved through a combination of facility design, optic support structure design, and passive damping. Thermal stability will be accomplished by using high thermal-mass concrete structures, conditioned air flow, and a reduction of heat sources. Finite element analysis has been used to evaluate the design of the TAB and optical support structures. A detailed structural model of the TAB that includes the target positioner, target chamber, turning mirrors, and diagnostics, has been used for stability evaluations. Finite element analyses covering ambient ground vibration, thermal loads, pressure fluctuations, and wind excitations have demonstrated that the current design of the TAB provides a stable platform for maintaining beam alignment.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.